Joints in the body have compartments with articulating surfaces that move against or in close proximity with other components in the joint. For example, the knee joint includes the distal femur that cooperates with both the patella and proximal tibia and, if present, a fabella. The distal femur has a lateral and medial condyle that rotates in moving relationship to the lateral and medial meniscus of the tibia. Bone disease, such as arthritis, may deteriorate one or more joint compartments so that movement in the joint produces pain. One remedy for joints deteriorated by disease or injury is replacement of one or more compartments of the joint with artificial implants. For example, a total knee replacement (TKR) may be performed by surgically opening the knee, removing the diseased portions of the distal femur, proximal tibia, and/or pattelar surface, and implanting an artificial prosthesis. The bio-compatible materials used to make the bone prosthesis reduce the risk of infection and wear well.
One important aspect of using artificial implants to repair a diseased joint is the fit of the artificial implants with one another and the patient's joint physiology. That is, implant size, shape, and location are important parameters for enabling patient movement that complies with the ligaments and muscles of the patient. Producing implants with the appropriate parameter values may determine whether a patient regains full function and mobility in the joint following the replacement surgery. Ideally, the components for a joint replacement would be customized for a patient's particular joint physiology. However, customizing every artificial implant component for a replacement surgery would significantly increase the cost of fabrication and coordination of component production with surgical resources would be difficult.
One way of addressing the need to provide artificial implants that can be accommodated by a patient's physiology is to provide a finite number of artificial implants that accommodate a range of characteristics for the bones of commonly replaced joints. To design these artificial implant models, statistical data regarding the measurements of bone dimensions are collected for a sample population to determine the range and variability of bone dimensions that need to be accommodated in the general population. A hospital or surgery center may then keep an inventory of the various joint implant models to be ready to meet the needs of the patients undergoing joint replacement surgery.
One problem with this approach is the fit required for a complete range of motion for the joint. The natural variations in joints among people and the abundance of soft tissue structures for an indeterminate multiplicity of load sharing possibilities result in measurably different movements. An artificial implant must work together with a patient's soft tissues so a joint may achieve its proper motion. Thus, the artificial implant should closely represent a patient's articular geometry.
What is needed is a way of designing artificial implant components so that physiological movement is incorporated in the design and dimensions of the artificial implants.
What is needed is a way of designing artificial implants so that dynamic movement of a joint does not interfere with the smooth operation of articulating surfaces of artificial implants.